Cobalt powder suitable for use as the cementing agent in refractory carbides is in short supply. Pure cobalt material, however, is readily available. There are no known good methods to convert pure cobalt to powder in an economical manner. The high purity of cobalt causes acid dissolution to be unreasonably slow and to require a large excess of acid for complete dissolution. Although a chemical process based on dissolution, e.g. concentrated hydrochloric acid can be operated in the laboratory, this is not feasible for a commercial operation.
U.S. Pat. No. 3,595,484 relates to a process for reclaiming refractory carbide scrap which contains cobalt as a cementing agent in the 5 to 15 weight percent range. The carbide scrap is treated with molten zinc at a temperature in the range of 750.degree. C. to 850.degree. C. The zinc penetrates the cobalt and breaks the bond between the carbides and the cobalt. Subsequently the zinc is distilled off in a vacuum, leaving the carbide-cobalt mixture in a spongy condition, and amenable to grinding to a powder for reuse in carbide preparation. The weight ratio of zinc to cobalt in the cemented carbide is in the range of 30:1 to 10:1, although at least 15:1 is preferred.
If the above described zinc process for reclaiming carbide scrap is applied to the conversion of pure cobalt to a more usable form, the amount of zinc required is quite excessive. For example, to process one pound of cobalt would require about 15 pounds of zinc. While the zinc is subsequently recovered via vacuum distillation and collection, at least two disadvantages are the result. First, the amount of cobalt that can be processed in a batch is very small for the size furnace, molds, etc. that are required, and, secondly, an excessive amount of energy must be consumed in heating, melting, and evaporating this large excess of zinc, and this large amount of energy must also be removed during condensation, freezing, and cooling of the distilled zinc.
An economically feasible method to convert pure cobalt to cobalt powder would be advantageous.